Brake



' Oct. 29 1940. L. A. CHAMINADE 2,219,764

BRAKE- Filed Sept. 16, 1939 2 Sheets-Sheet l Zinnntor I 4 022 lazazkmde/ Patented 29,

UNITED j STATES BRAKE 4 Leon A. Chamin'ade, Birmingham, Mich assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Application September 16, 1939, Serial No 295,221

. Claims.

This invention relates to brakes of the drum and shoe type and has been designed as a brake to retard the travel of vehicles.

I An'object of the invention is to improve the means by which a pair of shoes, each self. energizing for each direction of drum rotation, may be applied equally by mechanical linkage actuated by'a service pedal or by an emergency lever in cases where the shoes are normally actuated by the service pedal through the use'of other applying means such as a conventionahhydraulic brake applying system.

' Another object is the accomplishment of the major object by a construction which is eflicient,

simple and comparatively inexpensive.

Other objects and advantages will be understood from the'description which follows.

On the accompanying drawings:

Figure 1 is a transverse section through a stood that an equivalent of cover i5 will be secured to the steering knuckle in the case of front wheel brakes. Within the drum are shoes 2| and 23 which together occupy the greater part'of the arc of the flange 1. The shoes have webs 25, andflanges 21 carrying friction facings 29. One pair of adjacent she? ends are markedby numerals 2| and 23', he other pair by numerals 2|" and 23". Between the pairs of adjacent ends are wheel cylinders SI and 3| constituting parts of a hydraulic brake system. These wheel cylinders are secured to the backing plate. In the case of each cylinder there is a cap-shaped plunger 33 at one end. These plungers are adapted to be moved by a piston not shown and they contact diametrically opposite shoe ends 2| and 23". The shoe ends 2| and 23 are pushed outwardly by similar plungers 33'. These plungers 33', also advanced by pistons, do not -directly engage the shoe ends but they have adjustable threaded connections. with members 35 which engage the shoe ends. Retracting springs 81 function'lto withdrawthe shoes from the drum surface, the movement being limited by the enderends to take the braking torque. Since each shoe may anchor at eitherend and since the apequalizer.

gagement of the plungers 33, 33' with the ends of the cylinders.

While other forms of anchorage may be used,

the embodiment illustrated uses the wheel cylinplying force is applied to both pairs of adjacent ends, the brake is fully self energizing. Each shoe being subject to the energizing effect of the rotating drum for each direction of drum rotae tion. When the brake is applied with the drum rotating counterclockwise -shoe.2|' anchors at its end 2| which pushes plunger 33 against cylinder 3|. At the same time shoe end 23" anchors on cylinder 3|. For clockwise rotation the other shoe ends anchor and the first mentioned ends are moved away from the respectivecylinder I With the above construction there is also provided a mechanical linkage for applying the brakes so that they may operate in precisely the same way; so that the mechanically applied force shall be equalized; so that each shoe may anchor at one or the other of its ends; and so that each may be self-energizing for each direction of drum rotation. To the end 2| of shoe 2| is pivoted at.

89 a lever 4|. To shoe end 2| is pivoted at a lever.45. At intermediate points of levers 4| and 45 are pivoted links 41 which are terminally pivoted to the shoe ends 23' and 23" as at 45. ,0 The free ends 49 and 5| of levers 4| and 45 are slidingly supported on faces. 53 on either side of the pivot center of an equalizer .55. -Escape oi the ends 49 and 5| from faces 53 is prevented by guards 51. The equalizer is medially pivoted at 59 to a lever arm 6| extending from a rockshaft I 83 :lournalled in cover l5. Outside the cover the rock shaft has an adjustable lever arm designated as a whole by numeral 65. Lever arm 65 is adapted to be connected to a suitable applying 0 plements the service system as shown by the drawings.

By the arrangement shown for mechanical operation the pairs of adjacent shoe ends are spread by the assembly of levers and links and the action is equalized by the equalizer 55. The shift of anchorage from one pair of diametrically opposite ends to the other-pair when checking 5 opposite. direction or drum rotation is provided by the sliding of lever ends 49 and 5| on the- .Iclaim:

1. In a brake, a rotatable drum, a cover, shoes is to frictionally engage said drum, means whereby one end oi! each shoe anchors for one direction of drum rotation and the other ends anchor for the opposite direction of drum rotation, a lever pivoted to, each end of one shoe, a link pivoted at one end to each end of the other shoe, the other .ends of said links pivoted to intermediate points -jacent each pair of adjacent shoe ends whereby said shoes may be spread into drum contact, said cylinders serving the further purpose of shoe anchors.

4. In a brake, a rotatable drum, 9. cover, shoes to frictionaliy engage said drum, means where- 5 by one end of each shoe anchors for one direction of drum rotation and the other ends anchor for the opposite direction of drum rotation, a lever pivoted to each end of one shoe, a link pivoted at one end to each end of the other shoe, the other ends of said links pivoted to intermediate points of said levers, a floating equalizer slidably engaging the otherwise free ends of said levers and means to move said equalizer to spread said shoes into contact with said drum, said last named means comprising a rock shaft journalled in said cover, a lever armsecured thereto outside said drum and cover enclosure whereby said rock shaft may. be rotated, a second arm on said rock shaft within the d enclosure, said second arm being pivoted to said equalizer.

5. In a brake, a rotatable drum, a fixed cover, shoes having two pairs of adjacent ends, said shoes being operable to frictionally engage said drum, levers terminally pivoted to the ends of one shoe, links terminally pivoted to the ends of the other shoe and also pivoted to intermediate points of said levers, the remaining andadjacent ends of said levers being spaced, a floating equalizer engaged by the free spaced ends of said levers, means to move said equalizer and spread said shoes, means adjacent each pair or adjacent shoe ends and secured to said cover to receive brake torque from one or the other of said shoes dependent upon the direction of drum rotation,

at least one of said torque receiving means comprising a hydraulic brake applying cylinder.

' LEON A. CHAMINADE. 

